A relative of a missing six-year-old boy with autism in Lynnwood, Washington, on Tuesday, confessed to killing the child to the Snohomish County Sheriff's Office by drowning the boy in a bathtub, putting the body in a box and then throwing it in a dumpster.

The 19-year-old man, who was visiting family in Lynnwood, was booked on charges of first degree murder after David Pakko’s body was discovered the same day in the dumpster.

Pakko was reported missing from his apartment complex in the 15700 block of 44th Avenue West on Monday afternoon around 5 p.m. EDT. Sheriff's office spokeswoman Shari Ireton said Pakko had stayed home from school on Monday because he was sick. His mother was at work, when Pakko was said to have disappeared from the residence.

Pakko's body was found by the police just before 2 a.m. EDT Tuesday in a dumpster around the corner from the front door of their apartment where Pakko and his mother lived.

The sheriff's office said there was evidence that Pakko was a victim of homicide.

Police said Pakko was reportedly under adult supervision when was at home, and the sheriff’s department said that the 19-year-old suspect in custody was the same person watching Pakko before the 6-year-old disappeared on Monday, according to the CW affiliate, KTLA 5 News.

"[Name redacted] admitted, during that time, to filling a bathtub with water with the intention of drowning and killing D.P. [name redacted] admitted to calling D.P. to the bathroom, picking him up and placing him face down in the water, and holding D.P.’s head underneath the water while D.P. struggled for approximately 30 seconds before becoming still," the statement read. “[Name redacted] said he left D.P. face down in the water for approximately six minutes."

Ireton said there have been no other suspects in the case yet.

The principal of Beverly Elementary School in Lynnwood, where Pakko used to study in first grade, wrote in a letter to families that the school would be providing additional counselors and guest teachers in order to support students, staff, and parents.

"David was a vivacious, loving, determined 6-year-old who will be missed by his fellow first-graders, as well as classmates across all grades," Principal Danielle Sanders wrote, according to NBC affiliate King5.com. "His untimely death has reached the hearts of many throughout the region."

Cause and manner of death are yet to be determined by the medical examiner. The motive of the alleged murder was not mentioned in any report.

A memorial of flowers and candles had been growing outside Bristol Square apartments by Tuesday evening, where Pakko lived. Dozens of people had dropped off candles, balloons, notes and flowers at the memorial.

Samantha Burden, one of the residents in the apartment, has an 8-year-old son Kaedyn, who was friends with the victim. 

"We used to wrestle and play," Kaedyn said. 

Burden also said the kids often played together at the playground. "Just thinking about what [David] went through, it's just disgusting," she said. 

Phillip Edwards, a friend of the Pakko family, described the child as an "energetic, sweet boy" after the tragic incident.

"He loved Legos, he was brilliant. Smart as a whip," Edwards said, "I don't understand why a person could go through such lengths with such a small child,” according to CBS affiliate KIRO-7 News.